Redox control of glutamine utilization in cancer

GLS and GLS2 Glutaminase Isoenzymes in the Antioxidant System of Cancer Cells

A pathway frequently altered in cancer is glutaminolysis, whereby glutaminase (GA) catalyzes the main step as follows: the deamidation of glutamine to form glutamate and ammonium. There are two types of GA isozymes, named GLS and GLS2, which differ considerably in their expression patterns and can even perform opposing roles in cancer. GLS correlates with tumor growth and proliferation, while GLS2 can function as a context-dependent tumor suppressor. However, both isoenzymes have been described as essential molecules handling oxidant stress because of their involvement in glutathione production. We reviewed the literature to highlight the critical roles of GLS and GLS2 in restraining ROS and regulating both cellular signaling and metabolic stress due to their function as indirect antioxidant enzymes, as well as by modulating both reductive carboxylation and ferroptosis. Blocking GA activity appears to be a potential strategy in the dual activation of ferroptosis and inhibition of cancer cell growth in a ROS-mediated mechanism.

Transient kinetics reveal the mechanism of competitive inhibition of the neutral amino acid transporter ASCT2

ASCT2 (alanine serine cysteine transporter 2), a member of the solute carrier 1 family, mediates Na+-dependent exchange of small neutral amino acids across cell membranes. ASCT2 was shown to be highly expressed in tumor cells, making it a promising target for anticancer therapies. In this study, we explored the binding mechanism of the high-affinity competitive inhibitor L-cis hydroxyproline biphenyl ester (Lc-BPE) with ASCT2, using electrophysiological and rapid kinetic methods. Our investigations reveal that Lc-BPE binding requires one or two Na+ ions initially bound to the apo-transporter with high affinity, with Na1 site occupancy being more critical for inhibitor binding. In contrast to the amino acid substrate bound form, the final, third Na+ ion cannot bind, due to distortion of its binding site (Na2), thus preventing the formation of a translocation-competent complex. Based on the rapid kinetic analysis, the application of Lc-BPE generated outward transient currents, indicating that despite its net neutral nature, the binding of Lc-BPE in ASCT2 is weakly electrogenic, most likely because of asymmetric charge distribution within the amino acid moiety of the inhibitor. The preincubation with Lc-BPE also led to a decrease of the turnover rate of substrate exchange and a delay in the activation of substrate-induced anion current, indicating relatively slow Lc-BPE dissociation kinetics. Overall, our results provide new insight into the mechanism of binding of a prototypical competitive inhibitor to the ASCT transporters.

Glutaminolysis inhibition boosts photodynamic therapy to eliminate cancer stem cells

High reactive oxygen species (ROS) levels provide a therapeutic opportunity to eradicate cancer stem cells (CSCs), a population of cells responsible for tumorigenesis, progression, metastasis, and recurrence. However, enhanced antioxidant systems in this population of cells attenuate ROS-inducing therapies. Here, we developed a nanoparticle-assisted combination therapy to eliminate CSCs by employing photodynamic therapy (PDT) to yield ROS while disrupting ROS defense with glutaminolysis inhibition. Specifically, we leveraged an oleic acid-hemicyanine conjugate (CyOA) as photosensitizer, a new entity molecule HYL001 as glutaminolysis inhibitor, and a biocompatible folic acid-hydroxyethyl starch conjugate (FA-HES) as amphiphilic surfactant to construct cellular and mitochondrial hierarchical targeting nanomedicine (COHF NPs). COHF NPs inhibited glutaminolysis to reduce intracellular ROS scavengers, including glutathione (GSH) and nicotinamide adenine dinucleotide phosphate (NADPH), and to blunt oxidative phosphorylation (OXPHOS) for oxygen-conserved PDT. Compared to COLF NPs without glutaminolysis inhibitor, COHF NPs exhibited higher phototoxicity to breast cancer stem cells (BCSCs) both in vitro and in vivo. More importantly, we corroborated that marketed glutaminolysis inhibitors, such as CB839 and V9302, augment the clinically used photosensitizer (Hiporfin) for BCSCs elimination. This study develops a potent CSCs targeting strategy by combining glutaminolysis inhibition with PDT and provides significant implications for cancer therapy.

COVID-19 and Comorbidities: What Has Been Unveiled by Metabolomics?

The COVID-19 pandemic has brought about diverse impacts on the global population. Individuals with comorbidities were more susceptible to the severe symptoms caused by the virus. Within the crisis scenario, metabolomics represents a potential area of science capable of providing relevant information for understanding the metabolic pathways associated with the intricate interaction between the viral disease and previous comorbidities. This work aims to provide a comprehensive description of the scientific production pertaining to metabolomics within the specific context of COVID-19 and comorbidities, while highlighting promising areas for exploration by those interested in the subject. In this review, we highlighted the studies of metabolomics that indicated a variety of metabolites associated with comorbidities and COVID-19. Furthermore, we observed that the understanding of the metabolic processes involved between comorbidities and COVID-19 is limited due to the urgent need to report disease outcomes in individuals with comorbidities. The overlap of two or more comorbidities associated with the severity of COVID-19 hinders the comprehension of the significance of each condition. Most identified studies are observational, with a restricted number of patients, due to challenges in sample collection amidst the emergent situation.

Targeting glutamine metabolism exhibits anti-tumor effects in thyroid cancer

BACKGROUND

Effective treatment for patients with advanced thyroid cancer is lacking. Metabolism reprogramming is required for cancer to undergo oncogenic transformation and rapid tumorigenic growth. Glutamine is frequently used by cancer cells for active bioenergetic and biosynthetic needs. This study aims to investigate whether targeting glutamine metabolism is a promising therapeutic strategy for thyroid cancer.

METHODS

The expression of glutaminase (GLS) and glutamate dehydrogenase (GDH) in thyroid cancer tissues was evaluated by immunohistochemistry, and glutamine metabolism-related genes were assessed using real time-qPCR and western blotting. The effects of glutamine metabolism inhibitor 6-diazo-5-oxo-l-norleucine (DON) on thyroid cancer cells were determined by CCK-8, clone formation assay, Edu incorporation assay, flow cytometry, and Transwell assay. The mechanistic study was performed by real time-qPCR, western blotting, Seahorse assay, and gas chromatography-mass spectrometer assay. The effect of DON prodrug (JHU-083) on thyroid cancer in vivo was assessed using xenograft tumor models in BALB/c nude mice.

RESULTS

GLS and GDH were over-expressed in thyroid cancer tissues, and GLS expression was positively associated with lymph-node metastasis and TNM stage. The growth of thyroid cancer cells was significantly inhibited when cultured in glutamine-free medium. Targeting glutamine metabolism with DON inhibited the proliferation of thyroid cancer cells. DON treatment did not promote apoptosis, but increased the proportion of cells in the S phase, accompanied by the decreased expression of cyclin-dependent kinase 2 and cyclin A. DON treatment also significantly inhibited the migration and invasion of thyroid cancer cells by reducing the expression of N-cadherin, Vimentin, matrix metalloproteinase-2, and matrix metalloproteinase-9. Non-essential amino acids, including proline, alanine, aspartate, asparagine, and glycine, were reduced in thyroid cancer cells treated with DON, which could explain the decrease of proteins involved in migration, invasion, and cell cycle. The efficacy and safety of DON prodrug (JHU-083) for thyroid cancer treatment were verified in a mouse model. In addition to suppressing the proliferation and metastasis potential of thyroid cancer in vivo, enhanced innate immune response was also observed in JHU-083-treated xenograft tumors as a result of decreased expression of cluster of differentiation 47 and programmed cell death ligand 1.

CONCLUSIONS

Thyroid cancer exhibited enhanced glutamine metabolism, as evidenced by the glutamine dependence of thyroid cancer cells and high expression of multiple glutamine metabolism-related genes. Targeting glutamine metabolism with DON prodrug could be a promising therapeutic option for advanced thyroid cancer.

Metabolic Signature of Warburg Effect in Cancer: An Effective and Obligatory Interplay between Nutrient Transporters and Catabolic/Anabolic Pathways to Promote Tumor Growth

Aerobic glycolysis in cancer cells, originally observed by Warburg 100 years ago, which involves the production of lactate as the end product of glucose breakdown even in the presence of adequate oxygen, is the foundation for the current interest in the cancer-cell-specific reprograming of metabolic pathways. The renewed interest in cancer cell metabolism has now gone well beyond the original Warburg effect related to glycolysis to other metabolic pathways that include amino acid metabolism, one-carbon metabolism, the pentose phosphate pathway, nucleotide synthesis, antioxidant machinery, etc. Since glucose and amino acids constitute the primary nutrients that fuel the altered metabolic pathways in cancer cells, the transporters that mediate the transfer of these nutrients and their metabolites not only across the plasma membrane but also across the mitochondrial and lysosomal membranes have become an integral component of the expansion of the Warburg effect. In this review, we focus on the interplay between these transporters and metabolic pathways that facilitates metabolic reprogramming, which has become a hallmark of cancer cells. The beneficial outcome of this recent understanding of the unique metabolic signature surrounding the Warburg effect is the identification of novel drug targets for the development of a new generation of therapeutics to treat cancer.

Glutamine addiction in tumor cell: oncogene regulation and clinical treatment

After undergoing metabolic reprogramming, tumor cells consume additional glutamine to produce amino acids, nucleotides, fatty acids, and other substances to facilitate their unlimited proliferation. As such, the metabolism of glutamine is intricately linked to the survival and progression of cancer cells. Consequently, targeting the glutamine metabolism presents a promising strategy to inhibit growth of tumor cell and cancer development. This review describes glutamine uptake, metabolism, and transport in tumor cells and its pivotal role in biosynthesis of amino acids, fatty acids, nucleotides, and more. Furthermore, we have also summarized the impact of oncogenes like C-MYC, KRAS, HIF, and p53 on the regulation of glutamine metabolism and the mechanisms through which glutamine triggers mTORC1 activation. In addition, role of different anti-cancer agents in targeting glutamine metabolism has been described and their prospective applications are assessed.

Upregulation of BRCA1 and 2 protein expression is associated with dysregulation in amino acids profiles in breast cancer

BACKGROUND

The prevalence of breast cancer (BC) is high among cancers in Egypt, ranking it the most common cause of cancer mortality in women. BRCA1 and BRCA2 tumor suppressors proteins have a specific relationship with BC. Plasma free amino acids levels (PFAAs) have been reported to exhibit altered profiles among cancer patients. Thus, the present study aims to examine the alteration of the PFAAs profiles and investigate their association with BRCA1 and 2 circulating levels in Egyptian females diagnosed with BC and in females with family history of BC to establish potential early detection strategies for BC.

METHODS AND RESULTS

This study included 26 BC patients, 22 females with family history of BC (relatives) in addition to 38 healthy females as control group. Quantitative measurement of PFAAs was determined by the ion exchange separation method through high performance liquid chromatography. BRCA1 and BRCA2 concentrations were determined using ELISA. Our results showed PFAAs profiles in BC patients and in females with BC family history with significant upregulation in mean plasma levels of Alanine, Phenylalanine, Glutamate and Cysteine and downregulation of Taurine, Threonine, Serine, Glycine, Valine, Methionine and Histidine levels compared to controls. Also, a significant positive correlation was observed between plasma BRCA1 and Valine levels while a significant negative correlation was observed between BRCA2 and Lysine plasma levels.

CONCLUSION

PFAAs profile can potentially be used in early screening for BC patients and for susceptible females.

Post-translational modulation of cell signalling through protein succinylation

Cells need to adapt their activities to extra- and intracellular signalling cues. To translate a received extracellular signal, cells have specific receptors that transmit the signal to downstream proteins so that it can reach the nucleus to initiate or repress gene transcription. Post-translational modifications (PTMs) of proteins are reversible or irreversible chemical modifications that help to further modulate protein activity. The most commonly observed PTMs are the phosphorylation of serine, threonine, and tyrosine residues, followed by acetylation, glycosylation, and amidation. In addition to PTMs that involve the modification of a certain amino acid (phosphorylation, hydrophobic groups for membrane localisation, or chemical groups like acylation), or the conjugation of peptides (SUMOylation, NEDDylation), structural changes such as the formation of disulphide bridge, protein cleavage or splicing can also be classified as PTMs. Recently, it was discovered that metabolites from the tricarboxylic acid (TCA) cycle are not only intermediates that support cellular metabolism but can also modify lysine residues. This has been shown for acetate, succinate, and lactate, among others. Due to the importance of mitochondria for the overall fitness of organisms, the regulatory function of such PTMs is critical for protection from aging, neurodegeneration, or cardiovascular disease. Cancer cells and activated immune cells display a phenotype of accelerated metabolic activity known as the Warburg effect. This metabolic state is characterised by enhanced glycolysis, the use of the pentose phosphate pathway as well as a disruption of the TCA cycle, ultimately causing the accumulation of metabolites like citrate, succinate, and malate. Succinate can then serve as a signalling molecule by directly interacting with proteins, by binding to its G protein-coupled receptor 91 (GPR91) and by post-translationally modifying proteins through succinylation of lysine residues, respectively. This review is focus on the process of protein succinylation and its importance in health and disease.

Attenuating Colorectal Cancer Using Nine Cultivars of Australian Lupin Seeds: Apoptosis Induction Triggered by Mitochondrial Reactive Oxygen Species Generation and Caspases-3/7 Activation

As Australian lupin cultivars are rich sources of polyphenols, dietary fibers, high-quality proteins, and abundant bioactive compounds with significant antioxidant, antidiabetic, and anticancer activities, this research work is aimed at investigating the colon cancer alleviation activity of nine cultivars of lupin seeds on HCT116 and HT29 colon carcinoma cell lines through anti-proliferation assay, measurement of apoptosis, and identification of the mechanism of apoptosis. Nine cultivars were pre-screened for anti-proliferation of HCT116 and HT29 cells along with consideration of the impact of heat processing on cancer cell viability. Mandelup and Jurien showed significant inhibition of HCT116 cells, whereas the highest inhibition of HT29 cell proliferation was attained by Jurien and Mandelup. Processing decreased the anti-proliferation activity drastically. Lupin cultivars Mandelup, Barlock, and Jurien (dose: 300 μg/mL) induced early and late apoptosis of colon cancer cells in Annexin V-FITC assay. The mechanism of apoptosis was explored, which involves boosting of caspases-3/7 activation and intracellular reactive oxygen species (ROS) generation in HCT116 cells (Mandelup and Barlock) and HT29 cells (Jurien and Mandelup). Thus, the findings showed that lupin cultivars arrest cell cycles by inducing apoptosis of colorectal carcinoma cells triggered by elevated ROS generation and caspases-3/7 activation.

Intratumoral metabolic heterogeneity of colorectal cancer

Although the metabolic phenotype within tumors is known to differ significantly from that of the surrounding normal tissue, the importance of this heterogeneity is just becoming widely recognized. Colorectal cancer (CRC) is often classified as the Warburg phenotype, a metabolic type in which the glycolytic system is predominant over oxidative phosphorylation (OXPHOS) in mitochondria for energy production. However, this dichotomy (glycolysis vs. OXPHOS) may be too simplistic and not accurately represent the metabolic characteristics of CRC. Therefore, in this review, we decompose metabolic phenomena into factors based on their source/origin and reclassify them into two categories: extrinsic and intrinsic. In the CRC context, extrinsic factors include those based on the environment, such as hypoxia, nutrient deprivation, and the tumor microenvironment, whereas intrinsic factors include those based on subpopulations, such as pathological subtypes and cancer stem cells. These factors form multiple layers inside and outside the tumor, affecting them additively, dominantly, or mutually exclusively. Consequently, the metabolic phenotype is a heterogeneous and fluid phenomenon reflecting the spatial distribution and temporal continuity of these factors. This allowed us to redefine the characteristics of specific metabolism-related factors in CRC and summarize and update our accumulated knowledge of their heterogeneity. Furthermore, we positioned tumor budding in CRC as an intrinsic factor and a novel form of metabolic heterogeneity, and predicted its metabolic dynamics, noting its similarity to circulating tumor cells and epithelial-mesenchymal transition. Finally, the possibilities and limitations of using human tumor tissue as research material to investigate and assess metabolic heterogeneity are discussed.

Rewiring of mitochondrial metabolism in therapy-resistant cancers: permanent and plastic adaptations

Deregulation of tumor cell metabolism is widely recognized as a "hallmark of cancer." Many of the selective pressures encountered by tumor cells, such as exposure to anticancer therapies, navigation of the metastatic cascade, and communication with the tumor microenvironment, can elicit further rewiring of tumor cell metabolism. Furthermore, phenotypic plasticity has been recently appreciated as an emerging "hallmark of cancer." Mitochondria are dynamic organelles and central hubs of metabolism whose roles in cancers have been a major focus of numerous studies. Importantly, therapeutic approaches targeting mitochondria are being developed. Interestingly, both plastic (i.e., reversible) and permanent (i.e., stable) metabolic adaptations have been observed following exposure to anticancer therapeutics. Understanding the plastic or permanent nature of these mechanisms is of crucial importance for devising the initiation, duration, and sequential nature of metabolism-targeting therapies. In this review, we compare permanent and plastic mitochondrial mechanisms driving therapy resistance. We also discuss experimental models of therapy-induced metabolic adaptation, therapeutic implications for targeting permanent and plastic metabolic states, and clinical implications of metabolic adaptations. While the plasticity of metabolic adaptations can make effective therapeutic treatment challenging, understanding the mechanisms behind these plastic phenotypes may lead to promising clinical interventions that will ultimately lead to better overall care for cancer patients.

SLC1A5 regulates cell proliferation and self-renewal through β-catenin pathway mediated by redox signaling in arsenic-treated uroepithelial cells

Arsenic exposure increases the risk of bladder cancer in humans, but its underlying mechanisms remain elusive. The alanine, serine, cysteine-preferring transporter 2 (ASCT2, SLC1A5) is frequently overexpressed in cancer cells. The aim of this study was to evaluate the effects of arsenic on SLC1A5, and to determine the role of SLC1A5 in the proliferation and self-renewal of uroepithelial cells. F344 rats were exposed to 87 mg/L NaAsO₂ or 200 mg/L DMA^V for 12 weeks. The SV-40 immortalized human uroepithelial (SV-HUC-1) cells were cultured in medium containing 0.5 μM NaAsO₂ for 40 weeks. Arsenic increased the expression levels of SLC1A5 and β-catenin both in vivo and in vitro. SLC1A5 promoted cell proliferation and self-renewal by activating β-catenin, which in turn was dependent on maintaining GSH/ROS homeostasis. Our results suggest that SLC1A5 is a potential therapeutic target for arsenic-induced proliferation and self-renewal of uroepithelial cells.

Mechanisms of and Potential Medications for Oxidative Stress in Ovarian Granulosa Cells: A Review

Granulosa cells are essential for follicle initiation and development, and their abnormal function or apoptosis is a crucial factor leading to follicular atresia. A state of oxidative stress occurs when the balance between the production of reactive oxygen species and the regulation of the antioxidant system is disturbed. Oxidative stress is one of the most important causes of the abnormal function and apoptosis of granulosa cells. Oxidative stress in granulosa cells causes female reproductive system diseases, such as polycystic ovary syndrome and premature ovarian failure. In recent years, studies have confirmed that the mechanism of oxidative stress in granulosa cells is closely linked to the PI3K-AKT signaling pathway, MAPK signaling pathway, FOXO axis, Nrf2 pathway, NF-κB signaling pathway, and mitophagy. It has been found that drugs such as sulforaphane, Periplaneta americana peptide, and resveratrol can mitigate the functional damage caused by oxidative stress on granulosa cells. This paper reviews some of the mechanisms involved in oxidative stress in granulosa cells and describes the mechanisms underlying the pharmacological treatment of oxidative stress in granulosa cells.

Mitochondrial supercomplex assembly regulates metabolic features and glutamine dependency in mammalian cells

Rationale: Mitochondria generate ATP via the oxidative phosphorylation system, which mainly comprises five respiratory complexes found in the inner mitochondrial membrane. A high-order assembly of respiratory complexes is called a supercomplex. COX7A2L is a supercomplex assembly factor that has been well-investigated for studying supercomplex function and assembly. To date, the effects of mitochondrial supercomplexes on cell metabolism have not been elucidated. Methods: We depleted COX7A2L or Cox7a2l in human and mouse cells to generate cell models lacking mitochondrial supercomplexes as well as in DBA/2J mice as animal models. We tested the effect of impaired supercomplex assembly on cell proliferation with different nutrient supply. We profiled the metabolic features in COX7A2L-/- cells and Cox7a2l-/- mice via the combined use of targeted and untargeted metabolic profiling and metabolic flux analysis. We further tested the role of mitochondrial supercomplexes in pancreatic ductal adenocarcinoma (PDAC) through PDAC cell lines and a nude mouse model. Results: Impairing mitochondrial supercomplex assembly by depleting COX7A2L in human cells reprogrammed metabolic pathways toward anabolism and increased glutamine metabolism, cell proliferation and antioxidative defense. Similarly, knockout of Cox7a2l in DBA/2J mice promoted the use of proteins/amino acids as oxidative carbon sources. Mechanistically, impaired supercomplex assembly increased electron flux from CII to CIII/CIV and promoted CII-dependent respiration in COX7A2L-/- cells which further upregulated glutaminolysis and glutamine oxidation to accelerate the reactions of the tricarboxylic acid cycle. Moreover, the proliferation of PDAC cells lacking COX7A2L was inhibited by glutamine deprivation. Conclusion: Our results reveal the regulatory role of mitochondrial supercomplexes in glutaminolysis which may fine-tune the fate of cells with different nutrient availability.

Role and therapeutic targeting of glutamine metabolism in non‑small cell lung cancer (Review)

The Warburg effect indicates that cancer cells survive through glycolysis under aerobic conditions; as such, the topic of cancer metabolism has aroused interest. It is requisite to further explore cancer metabolism, as it helps to simultaneously explain the process of carcinogenesis and guide therapy. The flexible metabolism of cancer cells, which is the result of metabolic reprogramming, can meet the basic needs of cells, even in a nutrition-deficient environment. Glutamine is the most abundant non-essential amino acid in the circulation, and along with glucose, comprise the two basic nutrients of cancer cell metabolism. Glutamine is crucial in non-small cell lung cancer (NSCLC) cells and serves an important role in supporting cell growth, activating signal transduction and maintaining redox homeostasis. In this perspective, the present review aims to provide a new therapeutic strategy of NSCLC through inhibiting the metabolism of glutamine. This review not only summarizes the significance of glutamine metabolism in NSCLC cells, but also enumerates traditional glutamine inhibitors along with new targets. It also puts forward the concept of combination therapy and patient stratification with the aim of comprehensively showing the effect and prospect of targeted glutamine metabolism in NSCLC therapy. This review was completed by searching for keywords including 'glutamine', 'NSCLC' and 'therapy' on PubMed, and screening out articles.

Reprogramming the tumor microenvironment with biotechnology

The tumor microenvironment (TME) is a unique environment that is developed by the tumor and controlled by tumor-induced interactions with host cells during tumor progression. The TME includes immune cells, which can be classified into two types: tumor- antagonizing and tumor-promoting immune cells. Increasing the tumor treatment responses is associated with the tumor immune microenvironment. Targeting the TME has become a popular topic in research, which includes polarizing macrophage phenotype 2 into macrophage phenotype 1 using Toll-like receptor agonists with cytokines, anti-CD47, and anti-SIPRα. Moreover, inhibiting regulatory T cells through blockades and depletion restricts immunosuppressive cells in the TME. Reprogramming T cell infiltration and T cell exhaustion improves tumor infiltrating lymphocytes, such as CD8⁺ or CD4⁺ T cells. Targeting metabolic pathways, including glucose, lipid, and amino acid metabolisms, can suppress tumor growth by restricting the absorption of nutrients and adenosine triphosphate energy into tumor cells. In conclusion, these TME reprogramming strategies exhibit more effective responses using combination treatments, biomaterials, and nanoparticles. This review highlights how biomaterials and immunotherapy can reprogram TME and improve the immune activity.

Metabolic Health, Mitochondrial Fitness, Physical Activity, and Cancer

Cancer continues to be a significant global health issue. Traditional genetic-based approaches to understanding and treating cancer have had limited success. Researchers are increasingly exploring the impact of the environment, specifically inflammation and metabolism, on cancer development. Examining the role of mitochondria in this context is crucial for understanding the connections between metabolic health, physical activity, and cancer. This study aimed to review the literature on this topic through a comprehensive narrative review of various databases including MedLine (PubMed), Cochrane (Wiley), Embase, PsychINFO, and CinAhl. The review highlighted the importance of mitochondrial function in overall health and in regulating key events in cancer development, such as apoptosis. The concept of "mitochondrial fitness" emphasizes the crucial role of mitochondria in cell metabolism, particularly their oxidative functions, and how proper function can prevent replication errors and regulate apoptosis. Engaging in high-energy-demanding movement, such as exercise, is a powerful intervention for improving mitochondrial function and increasing resistance to environmental stressors. These findings support the significance of considering the role of the environment, specifically inflammation and metabolism, in cancer development and treatment. Further research is required to fully understand the mechanisms by which physical activity improves mitochondrial function and potentially reduces the risk of cancer.

Metabolic Regulation Effect and Potential Metabolic Biomarkers of Pre-Treated Delphinidin on Oxidative Damage Induced by Paraquat in A549 Cells

Delphinidin (Del) is an anthocyanin component with high in vitro antioxidant capacity. In this study, based on the screening of a cell model, gas chromatography-time of flight mass spectrometry (GC-TOF/MS) was used to evaluate the effect of Del pre-protection on the metabolite levels of intracellular oxidative stress induced by paraquat (PQ). According to the cytotoxicity and reactive oxygen species (ROS) responses of four lung cell lines to PQ induction, A549 cell was selected and treated with 100 μM PQ for 12 h to develop a cellular oxidative stress model. Compared with the PQ-induced group, the principal components of the Del pretreatment group had significant differences, but not significant with the control group, indicating that the antioxidant activity of Del can be correlated to the maintenance of metabolite levels. Del preconditioning protects lipid-related metabolic pathways from the disturbance induced by PQ. In addition, the levels of amino acid- and energy-related metabolites were significantly recovered. Del may also exert an antioxidant effect by regulating glucose metabolism. The optimal combinations of biomarkers in the PQ-treatment group and Del-pretreatment group were alanine-valine-urea and alanine-galactose-glucose. Cell metabolome data provided characteristic fingerprints associated with the antioxidant activity of Del.

Farnesysltransferase Inhibitor Prevents Burn Injury-Induced Metabolome Changes in Muscle

Burn injury remains a significant public health issue worldwide. Metabolic derangements are a major complication of burn injury and negatively affect the clinical outcomes of severely burned patients. These metabolic aberrations include muscle wasting, hypermetabolism, hyperglycemia, hyperlactatemia, insulin resistance, and mitochondrial dysfunction. However, little is known about the impact of burn injury on the metabolome profile in skeletal muscle. We have previously shown that farnesyltransferase inhibitor (FTI) reverses burn injury-induced insulin resistance, mitochondrial dysfunction, and the Warburg effect in mouse skeletal muscle. To evaluate metabolome composition, targeted quantitative analysis was performed using capillary electrophoresis mass spectrometry in mouse skeletal muscle. Principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA), and hierarchical cluster analysis demonstrated that burn injury induced a global change in metabolome composition. FTI treatment almost completely prevented burn injury-induced alterations in metabolite levels. Pathway analysis revealed that the pathways most affected by burn injury were purine, glutathione, β-alanine, glycine, serine, and threonine metabolism. Burn injury induced a suppressed oxidized to reduced nicotinamide adenine dinucleotide (NAD⁺/NADH) ratio as well as oxidative stress and adenosine triphosphate (ATP) depletion, all of which were reversed by FTI. Moreover, our data raise the possibility that burn injury may lead to increased glutaminolysis and reductive carboxylation in mouse skeletal muscle.

Immunometabolism characteristics and a potential prognostic risk model associated with TP53 mutations in breast cancer

TP53, a gene with high-frequency mutations, plays an important role in breast cancer (BC) development through metabolic regulation, but the relationship between TP53 mutation and metabolism in BC remains to be explored. Our study included 1,066 BC samples from The Cancer Genome Atlas (TCGA) database, 415 BC cases from the Gene Expression Omnibus (GEO) database, and two immunotherapy cohorts. We identified 92 metabolic genes associated with TP53 mutations by differential expression analysis between TP53 mutant and wild-type groups. Univariate Cox analysis was performed to evaluate the prognostic effects of 24 TP53 mutation-related metabolic genes. By unsupervised clustering and other bioinformatics methods, the survival differences and immunometabolism characteristics of the distinct clusters were illustrated. In a training set from TCGA cohort, we employed the least absolute shrinkage and selection operator (LASSO) regression method to construct a metabolic gene prognostic model associated with TP53 mutations, and the GEO cohort served as an external validation set. Based on bioinformatics, the connections between risk score and survival prognosis, tumor microenvironment (TME), immunotherapy response, metabolic activity, clinical characteristics, and gene characteristics were further analyzed. It is imperative to note that our model is a powerful and robust prognosis factor in comparison to other traditional clinical features and also has high accuracy and clinical usefulness validated by receiver operating characteristic (ROC) and decision curve analysis (DCA). Our findings deepen our understanding of the immune and metabolic characteristics underlying the TP53 mutant metabolic gene profile in BC, laying a foundation for the exploration of potential therapies targeting metabolic pathways. In addition, our model has promising predictive value in the prognosis of BC.

Mitochondrial NAD(P)+ Transhydrogenase: From Molecular Features to Physiology and Disease

Significance: Proton-translocating NAD(P)⁺ transhydrogenase, also known as nicotinamide nucleotide transhydrogenase (NNT), catalyzes a reversible reaction coupling the protonmotive force across the inner mitochondrial membrane and hydride (H^-, a proton plus two electrons) transfer between the mitochondrial pools of NAD(H) and NADP(H). The forward NNT reaction is a source of NADPH in the mitochondrial matrix, fueling antioxidant and biosynthetic pathways with reductive potential. Despite the greater emphasis given to the net forward reaction, the reverse NNT reaction that oxidizes NADPH also occurs in physiological and pathological conditions. Recent Advances: NNT (dys)function has been linked to various metabolic pathways and disease phenotypes. Most of these findings have been based on spontaneous loss-of-function Nnt mutations found in the C57BL/6J mouse strain (Nnt^C57BL/6J mutation) and disease-causing Nnt mutations in humans. The present review focuses on recent advances based on the mouse Nnt^C57BL/6J mutation. Critical Issues: Most studies associating NNT function with disease phenotypes have been based on comparisons between different strains of inbred mice (with or without the Nnt^C57BL/6J mutation), which creates uncertainties over the actual contribution of NNT in the context of other potential genetic modifiers. Future Directions: Future research might contribute to understanding the role of NNT in pathological conditions and elucidate how NNT regulates physiological signaling through its forward and reverse reactions. The importance of NNT in redox balance and tumor cell proliferation makes it a potential target of new therapeutic strategies for oxidative-stress-mediated diseases and cancer. Antioxid. Redox Signal. 36, 864-884.

Glutaminolysis-ammonia-urea Cycle Axis, Non-alcoholic Fatty Liver Disease Progression and Development of Novel Therapies

The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide, reflecting the current epidemics of obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome. NAFLD is characterized by the accumulation of fat in the liver, and is known to be a cause of cirrhosis. Although many pathways have been proposed, the cause of NAFLD-linked fibrosis progression is still unclear, which posed challenges for the development of new therapies to prevent NASH-related cirrhosis and hepatocellular carcinoma. Cirrhosis is associated with activation of hepatic stellate cells (HSC) and accumulation of excess extracellular matrix proteins, and inhibiting the activation of HSCs would be expected to slow the progression of NAFLD-cirrhosis. Multiple molecular signals and pathways such as oxidative stress and glutaminolysis have been reported to promote HSC activation. Both mechanisms are plausible antifibrotic targets in NASH, as the activation of HSCs the proliferation of myofibroblasts depend on those processes. This review summarizes the role of the glutaminolysis-ammonia-urea cycle axis in the context of NAFLD progression, and shows how the axis could be a novel therapeutic target.

Therapeutic Potential of Glutamine Pathway in Lung Cancer

Cancer cells tend to obtain the substances needed for their development depending on altering metabolic characteristics. Among the reorganized metabolic pathways, Glutamine pathway, reprogrammed to be involved in the physiological process including energy supply, biosynthesis and redox homeostasis, occupies an irreplaceable role in tumor cells and has become a hot topic in recent years. Lung cancer currently maintains a high morbidity and mortality rate among all types of tumors and has been a health challenge that researchers have longed to overcome. Therefore, this study aimed to clarify the essential role of glutamine pathway played in the metabolism of lung cancer and its potential therapeutic value in the interventions of lung cancer.

Mitochondrial glutamine metabolism regulates sensitivity of cancer cells after chemotherapy via amphiregulin

The DNA damage response is essential for sustaining genomic stability and preventing tumorigenesis. However, the fundamental question about the cellular metabolic response to DNA damage remains largely unknown, impeding the development of metabolic interventions that might prevent or treat cancer. Recently, it has been reported that there is a link between cell metabolism and DNA damage response, by repression of glutamine (Gln) entry into mitochondria to support cell cycle arrest and DNA repair. Here, we show that mitochondrial Gln metabolism is a crucial regulator of DNA damage-induced cell death. Mechanistically, inhibition of glutaminase (GLS), the first enzyme for Gln anaplerosis, sensitizes cancer cells to DNA damage by inducing amphiregulin (AREG) that promotes apoptotic cell death. GLS inhibition increases reactive oxygen species production, leading to transcriptional activation of AREG through Max-like protein X (MLX) transcription factor. Moreover, suppression of mitochondrial Gln metabolism results in markedly increased cell death after chemotherapy in vitro and in vivo. The essentiality of this molecular pathway in DNA damage-induced cell death may provide novel metabolic interventions for cancer therapy.

Comorbidity-associated glutamine deficiency is a predisposition to severe COVID-19

SARS-CoV-2 vaccinations have greatly reduced COVID-19 cases, but we must continue to develop our understanding of the nature of the disease and its effects on human immunity. Previously, we suggested that a dysregulated STAT3 pathway following SARS-Co-2 infection ultimately leads to PAI-1 activation and cascades of pathologies. The major COVID-19-associated metabolic risks (old age, hypertension, cardiovascular diseases, diabetes, and obesity) share high PAI-1 levels and could predispose certain groups to severe COVID-19 complications. In this review article, we describe the common metabolic profile that is shared between all of these high-risk groups and COVID-19. This profile not only involves high levels of PAI-1 and STAT3 as previously described, but also includes low levels of glutamine and NAD+, coupled with overproduction of hyaluronan (HA). SARS-CoV-2 infection exacerbates this metabolic imbalance and predisposes these patients to the severe pathophysiologies of COVID-19, including the involvement of NETs (neutrophil extracellular traps) and HA overproduction in the lung. While hyperinflammation due to proinflammatory cytokine overproduction has been frequently documented, it is recently recognized that the immune response is markedly suppressed in some cases by the expansion and activity of MDSCs (myeloid-derived suppressor cells) and FoxP3+ Tregs (regulatory T cells). The metabolomics profiles of severe COVID-19 patients and patients with advanced cancer are similar, and in high-risk patients, SARS-CoV-2 infection leads to aberrant STAT3 activation, which promotes a cancer-like metabolism. We propose that glutamine deficiency and overproduced HA is the central metabolic characteristic of COVID-19 and its high-risk groups. We suggest the usage of glutamine supplementation and the repurposing of cancer drugs to prevent the development of severe COVID-19 pneumonia.

An NADH-selective and sensitive fluorescence probe to evaluate living cell hypoxic stress

Cellular disease and senescence are often accompanied by an imbalance in the local oxygen supply. Under hypoxia, mitochondrial NADH and FADH₂ cannot be oxidized by the mitochondrial electron transport chain, which leads to the accumulation of reducing equivalents and subsequent reduction stress. Detecting changes in intracellular NADH levels is expected to allow an assessment of stress. We synthesized a red fluorescent probe, DPMQL1, with high selectivity and sensitivity for detecting NADH in living cells. The probe DPMQL1 has strong anti-interference abilities toward various potential biological interferences, such as metal ions, anions, redox species, and other biomolecules. In addition, its detection limit can reach the nanomolar level, meaning it can display small changes in NADH levels in living cells, so as to realize the evaluation of cell-based hypoxic stress.

Metabolic Analysis of the Asparagine and Glutamine Dynamics in an Industrial CHO Fed-Batch Process

Chinese hamster ovary (CHO) cell lines are grown in cultures with varying asparagine and glutamine concentrations, but further study is needed to characterize the interplay between these amino acids. By following ¹³C‐glucose, ¹³C‐glutamine, and ¹³C‐asparagine tracers using metabolic flux analysis (MFA), CHO cell metabolism was characterized in an industrially relevant fed‐batch process under glutamine supplemented and low glutamine conditions during early and late exponential growth. For both conditions MFA revealed glucose as the primary carbon source to the tricarboxylic acid (TCA) cycle followed by glutamine and asparagine as secondary sources. Early exponential phase CHO cells prefer glutamine over asparagine to support the TCA cycle under the glutamine supplemented condition, while asparagine was critical for TCA activity for the low glutamine condition. Overall TCA fluxes were similar for both conditions due to the trade‐offs associated with reliance on glutamine and/or asparagine. However, glutamine supplementation increased fluxes to alanine, lactate and enrichment of glutathione, N‐acetyl‐glucosamine and pyrimidine‐containing‐molecules. The late exponential phase exhibited reduced central carbon metabolism dominated by glucose, while lactate reincorporation and aspartate uptake were preferred over glutamine and asparagine. These ¹³C studies demonstrate that metabolic flux is process time dependent and can be modulated by varying feed composition.

Mitochondria-Mediated Apoptosis of HCC Cells Triggered by Knockdown of Glutamate Dehydrogenase 1: Perspective for Its Inhibition through Quercetin and Permethylated Anigopreissin A

Metabolic reprogramming is a hallmark of cancer cells required to ensure high energy needs and the maintenance of redox balance. A relevant metabolic change of cancer cell bioenergetics is the increase in glutamine metabolism. Hepatocellular carcinoma (HCC), one of the most lethal cancer and which requires the continuous development of new therapeutic strategies, shows an up-regulation of human glutamate dehydrogenase 1 (hGDH1). GDH1 function may be relevant in cancer cells (or HCC) to drive the glutamine catabolism from L-glutamate towards the synthesis of α-ketoglutarate (α-KG), thus supplying key tricarboxylic acid cycle (TCA cycle) metabolites. Here, the effects of hGLUD1 gene silencing (siGLUD1) and GDH1 inhibition were evaluated. Our results demonstrate that siGLUD1 in HepG2 cells induces a significant reduction in cell proliferation (58.8% ± 10.63%), a decrease in BCL2 expression levels, mitochondrial mass (75% ± 5.89%), mitochondrial membrane potential (30% ± 7.06%), and a significant increase in mitochondrial superoxide anion (25% ± 6.55%) compared to control/untreated cells. The inhibition strategy leads us to identify two possible inhibitors of hGDH1: quercetin and Permethylated Anigopreissin A (PAA). These findings suggest that hGDH1 could be a potential candidate target to impair the metabolic reprogramming of HCC cells.

Transcriptomics and Metabolomics Integration Reveals Redox-Dependent Metabolic Rewiring in Breast Cancer Cells

Rewiring glucose metabolism toward aerobic glycolysis provides cancer cells with a rapid generation of pyruvate, ATP, and NADH, while pyruvate oxidation to lactate guarantees refueling of oxidized NAD⁺ to sustain glycolysis. CtPB2, an NADH-dependent transcriptional co-regulator, has been proposed to work as an NADH sensor, linking metabolism to epigenetic transcriptional reprogramming. By integrating metabolomics and transcriptomics in a triple-negative human breast cancer cell line, we show that genetic and pharmacological down-regulation of CtBP2 strongly reduces cell proliferation by modulating the redox balance, nucleotide synthesis, ROS generation, and scavenging. Our data highlight the critical role of NADH in controlling the oncogene-dependent crosstalk between metabolism and the epigenetically mediated transcriptional program that sustains energetic and anabolic demands in cancer cells.

More Than Meets the Eye Regarding Cancer Metabolism

In spite of the continuous improvement in our knowledge of the nature of cancer, the causes of its formation and the development of new treatment methods, our knowledge is still incomplete. A key issue is the difference in metabolism between normal and cancer cells. The features that distinguish cancer cells from normal cells are the increased proliferation and abnormal differentiation and maturation of these cells, which are due to regulatory changes in the emerging tumour. Normal cells use oxidative phosphorylation (OXPHOS) in the mitochondrion as a major source of energy during division. During OXPHOS, there are 36 ATP molecules produced from one molecule of glucose, in contrast to glycolysis which provides an ATP supply of only two molecules. Although aerobic glucose metabolism is more efficient, metabolism based on intensive glycolysis provides intermediate metabolites necessary for the synthesis of nucleic acids, proteins and lipids, which are in constant high demand due to the intense cell division in cancer. This is the main reason why the cancer cell does not "give up" on glycolysis despite the high demand for energy in the form of ATP. One of the evolving trends in the development of anti-cancer therapies is to exploit differences in the metabolism of normal cells and cancer cells. Currently constructed therapies, based on cell metabolism, focus on the attempt to reprogram the metabolic pathways of the cell in such a manner that it becomes possible to stop unrestrained proliferation.

Potential therapeutic treatments of cancer-induced bone pain

PURPOSE OF REVIEW

The treatment of cancer-induced bone pain (CIBP) has been proven ineffective and relies heavily on opioids, the target of highly visible criticism for their negative side effects. Alternative therapeutic agents are needed and the last few years have brought promising results, detailed in this review.

RECENT FINDINGS

Cysteine/glutamate antiporter system, xc, cannabinoids, kappa opioids, and a ceramide axis have all been shown to have potential as novel therapeutic targets without the negative effects of opioids.

SUMMARY

Review of the most recent and promising studies involving CIBP, specifically within murine models. Cancer pain has been reported by 30-50% of all cancer patients and even more in late stages, however the standard of care is not effective to treat CIBP. The complicated and chronic nature of this type of pain response renders over the counter analgesics and opioids largely ineffective as well as difficult to use due to unwanted side effects. Preclinical studies have been standardized and replicated while novel treatments have been explored utilizing various alternative receptor pathways: cysteine/glutamate antiporter system, xc, cannabinoid type 1 receptor, kappa opioids, and a ceramide axis sphingosine-1-phosphate/sphingosine-1-phosphate receptor 1.

ASCT1 and ASCT2: Brother and Sister?

The SLC1 family includes seven members divided into two groups, namely, EAATs and ASCTs, that share similar 3D architecture; the first one includes high-affinity glutamate transporters, and the second one includes SLC1A4 and SLC1A5, known as ASCT1 and ASCT2, respectively, responsible for the traffic of neutral amino acids across the cell plasma membrane. The physiological role of ASCT1 and ASCT2 has been investigated over the years, revealing different properties in terms of substrate specificities, affinities, and regulation by physiological effectors and posttranslational modifications. Furthermore, ASCT1 and ASCT2 are involved in pathological conditions, such as neurodegenerative disorders and cancer. This has driven research in the pharmaceutical field aimed to find drugs able to target the two proteins.This review focuses on structural, functional, and regulatory aspects of ASCT1 and ASCT2, highlighting similarities and differences.

Metabolic reprograming of antioxidant defense: a precision medicine perspective for radiotherapy of lung cancer?

Radiotherapy plays a key role in the management of lung cancer patients in curative and palliative settings. Traditionally, radiotherapy was either given alone or in combination with surgery, classical cytotoxic chemotherapy, or both. Technical and physical innovations achieved during the last two decades have helped to enhance the accuracy of radiotherapy dose delivery and have facilitated geometric radiotherapy individualization. Furthermore, multimodal combinations with molecularly tailored drugs or immunotherapy yielded promising survival benefits in selected patients. Yet high locoregional failure rates and frequent development of metastases still limit the patient outcome. One major obstacle to successful treatment is the high molecular heterogeneity observed in lung cancer. So far, clinical radiotherapy does not routinely use the knowledge on molecular subtypes with regard to therapy individualization and predictive biomarkers are missing. Herein, altered cancer metabolism has attracted novel attention during recent years as it promotes tumor growth and progression as well as resistance to anticancer therapies. The present perspective will exemplarily highlight how clinically relevant molecular subtypes defined by co-occurring somatic mutations in KRAS-driven lung cancer impact the metabolic phenotype of cancer cells, how the metabolic phenotype supports intrinsic radioresistance by the improved antioxidant defense, and also discuss potential subtype-specific actionable metabolic vulnerabilities. Understanding metabolic phenotypes of radioresistance and metabolic bottlenecks of cancer cells undergoing radiotherapy in a cancer-specific context will offer largely unexploited future avenues for biological individualization and optimization of radiotherapy. Transcriptional profiles will provide additional benefit in defining metabolic phenotypes associated with radioresistance, particularly in cases, where such dependencies cannot be identified by specific somatic mutations.

DDIT3 Directs a Dual Mechanism to Balance Glycolysis and Oxidative Phosphorylation during Glutamine Deprivation

Extracellular glutamine represents an important energy source for many cancer cells and its metabolism is intimately involved in maintaining redox homeostasis. The heightened metabolic activity within tumor tissues can result in glutamine deficiency, necessitating metabolic reprogramming responses. Here, dual mechanisms involving the stress-responsive transcription factor DDIT3 (DNA damage induced transcript 3) that establishes an interrelationship between glycolysis and mitochondrial respiration are revealed. DDIT3 is induced during glutamine deprivation to promote glycolysis and adenosine triphosphate production via suppression of the negative glycolytic regulator TIGAR. In concert, a proportion of the DDIT3 pool translocates to the mitochondria and suppresses oxidative phosphorylation through LONP1-mediated down-regulation of COQ9 and COX4. This in turn dampens the sustained levels of reactive oxygen species that follow glutamine withdrawal. Together these mechanisms constitute an adaptive survival mechanism permitting tumor cells to survive metabolic stress induced by glutamine starvation.

Pharmacological Vitamin C Treatment Impedes the Growth of Endogenous Glutamine-Dependent Cancers by Targeting Glutamine Synthetase

Purpose: Glutamine synthetase (GS) is the only currently known enzyme responsible for synthesizing endogenous glutamine (Gln). GS exerts a critical role in the oncogenesis of endogenous Gln-dependent cancers, making it an attractive target for anti-tumor therapies. A mixed-function oxidation system consisting of vitamin C (VC), oxygen, and trace metals can oxidize GS and promote its degradation. The current study aims to explore the effect of pharmacological VC treatment on GS.

Methods: Endogenous Gln-dependent cancer lines (breast cancer MCF7 and prostate cancer PC3) were selected to establish chronic Gln-deprived MCF7 and PC3 cell models. The expression of GS in parental and chronic Gln-deprived tumor cells exposed to VC treatment and control was determined by Western blot analysis. The anti-cancer effects of VC on parental and chronic Gln-deprived tumor cells were assessed by CCK-8 and annexin V-FITC/PI FACS assays. In addition, changes in cellular reactive oxygen species (ROS), glutathione (GSH) levels and NADPH/NADP + ratio were analyzed to explore the underlying mechanisms. Moreover, BALB/c nude mice xenografting with parental and chronic Gln-deprived prostate cancer cells were constructed to evaluate the in vivo therapeutic effect of VC. Finally, tumor 13N-ammonia uptake in mice bearing prostate cancer xenografts was analyzed following treatment with VC and the expression of GS in xenografts were detected by immunohistochemistry.

Results: Cells overexpressing GS were obtained by chronic Gln deprivation. We found that the cytotoxic effect of VC on cancer cells was positively correlated with the expression of GS. Additionally, VC treatment led to a significant increase in ROS production, as well as GSH depletion and NADPH/NADP + reduction. These changes could be reversed by the antioxidant N-acetyl-L-cysteine (NAC). Furthermore, pharmacological VC treatment exhibited a more significant therapeutic effect on xenografts of prostate cancer cells overexpressing GS, that could be well monitored by 13N-ammonia PET/CT imaging.

Conclusion: Our findings indicate that VC can kill cancer cells by targeting glutamine synthetase to induce oxidative stress. VC could be used as an anti-cancer treatment for endogenous glutamine-dependent cancers.

Kaempferol induces ROS-dependent apoptosis in pancreatic cancer cells via TGM2-mediated Akt/mTOR signaling

BACKGROUND

Kaempferol, a natural flavonoid, exhibits anticancer properties by scavenging reactive oxygen species (ROS). However, increasing evidence has demonstrated that, under certain conditions, kaempferol can inhibit tumor growth by upregulating ROS levels. In this study, we aimed to investigate whether kaempferol effectively suppresses pancreatic cancer through upregulation of ROS, and to explore the underlying molecular mechanism.

METHODS

PANC-1 and Mia PaCa-2 cells were exposed to different concentrations of kaempferol. Cell proliferation and colony formation were evaluated by CCK-8 and colony formation assays. Flow cytometry was performed to assess the ROS levels and cell apoptosis. The mRNA sequencing and KEGG enrichment analysis were performed to identify differentially expressed genes and to reveal significantly enriched signaling pathways in response to kaempferol treatment. Based on biological analysis, we hypothesized that tissue transglutaminase (TGM2) gene was an essential target for kaempferol to induce ROS-related apoptosis in pancreatic cancer. TGM2 was overexpressed by lentivirus vector to verify the effect of TGM2 on the ROS-associated apoptotic signaling pathway. Western blot and qRT-PCR were used to determine the protein and mRNA levels, respectively. The prognostic value of TGM2 was analyzed by Gene Expression Profiling Interactive Analysis (GEPIA) tools based on public data from the TCGA database.

RESULTS

Kaempferol effectively suppressed pancreatic cancer in vitro and in vivo. Kaempferol promoted apoptosis in vitro by increasing ROS generation, which was involved in Akt/mTOR signaling. TGM2 levels were significantly increased in PDAC tissues compared with normal tissues, and high TGM2 expression was positively correlated with poor prognosis in pancreatic cancer patients. Decreased TGM2 mRNA and protein levels were observed in the cells after treatment with kaempferol. Additionally, TGM2 overexpression downregulated ROS production and inhibited the abovementioned apoptotic signaling pathway.

CONCLUSIONS

Kaempferol induces ROS-dependent apoptosis in pancreatic cancer cells via TGM2-mediated Akt/mTOR signaling, and TGM2 may represent a promising prognostic biomarker for pancreatic cancer.

Revealing the Potential Application of EC-Synthetic Retinoid Analogues in Anticancer Therapy

(1) Background and Aim: All-trans retinoic acid (ATRA) induces differentiation and inhibits growth of many cancer cells. However, resistance develops rapidly prompting the urgent need for new synthetic and potent derivatives. EC19 and EC23 are two synthetic retinoids with potent stem cell neuro-differentiation activity. Here, these compounds were screened for their in vitro antiproliferative and cytotoxic activity using an array of different cancer cell lines. (2) Methods: MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, AV/PI (annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI)), cell cycle analysis, immunocytochemistry, gene expression analysis, Western blotting, measurement of glutamate and total antioxidant concentrations were recruited. (3) Results: HepG2, Caco-2, and MCF-7 were the most sensitive cell lines; HepG2 (ATRA; 36.2, EC19; 42.2 and EC23; 0.74 µM), Caco-2 (ATRA; 58.0, EC19; 10.8 and EC23; 14.7 µM) and MCF-7 (ATRA; 99.0, EC19; 9.4 and EC23; 5.56 µM). Caco-2 cells were selected for further biochemical investigations. Isobologram analysis revealed the combined synergistic effects with 5-fluorouracil with substantial reduction in IC₅₀. All retinoids induced apoptosis but EC19 had higher potency, with significant cell cycle arrest at subG₀-G₁, -S and G₂/M phases, than ATRA and EC23. Moreover, EC19 reduced cellular metastasis in a transwell invasion assay due to overexpression of E-cadherin, retinoic acid-induced 2 (RAI2) and Werner (WRN) genes. (4) Conclusion: The present study suggests that EC-synthetic retinoids, particularly EC19, can be effective, alone or in combinations, for potential anticancer activity to colorectal cancer. Further in vivo studies are recommended to pave the way for clinical applications.

Metabolic Reprogramming of Cancer by Chemicals that Target Glutaminase Isoenzymes

BACKGROUND

Metabolic reprogramming of tumours is a hallmark of cancer. Among the changes in the metabolic network of cancer cells, glutaminolysis is a key reaction altered in neoplasms. Glutaminase proteins control the first step in glutamine metabolism and their expression correlates with malignancy and growth rate of a great variety of cancers. The two types of glutaminase isoenzymes, GLS and GLS2, differ in their expression patterns and functional roles: GLS has oncogenic properties and GLS2 has been described as a tumour suppressor factor.

RESULTS

We have focused on glutaminase connections with key oncogenes and tumour suppressor genes. Targeting glutaminase isoenzymes includes different strategies aimed at deactivating the rewiring of cancer metabolism. In addition, we found a long list of metabolic enzymes, transcription factors and signalling pathways dealing with glutaminase. On the other hand, a number of chemicals have been described as isoenzyme-specific inhibitors of GLS and/or GLS2 isoforms. These molecules are being characterized as synergic and therapeutic agents in many types of tumours.

CONCLUSION

This review states the metabolic pathways that are rewired in cancer, the roles of glutaminase isoforms in cancer, as well as the metabolic circuits regulated by glutaminases. We also show the plethora of anticancer drugs that specifically inhibit glutaminase isoenzymes for treating several sets of cancer.

NDRG2 ablation reprograms metastatic cancer cells towards glutamine dependence via the induction of ASCT2

Background: Metastasis is the most common cause of lethal outcome in various types of cancers. Although the cell proliferation related metabolism rewiring has been well characterized, less is known about the association of metabolic changes with tumor metastasis. Herein, we demonstrate that metastatic tumor obtained a mesenchymal phenotype, which is obtained by the loss of tumor suppressor NDRG2 triggered metabolic switch to glutamine metabolism.

Methods: mRNA-seq and gene expression profile analysis were performed to define the differential gene expressions in primary MEC1 and metastatic MC3 cells and the downstream pathways of NDRG2. NDRG2 regulation of Fbw7-dependent c-Myc stability were determined by immunoprecipitation and protein half-life assay. Luciferase reporter and ChIP assays were used to determine the roles of Akt and c-Myc in mediating NDRG2-dependent regulation of ASCT2 in in both tumor and NDRG2-knockout MEF cells. Finally, the effect of the NDRG2/Akt/c-Myc/ASCT2 signaling on glutaminolysis and tumor metastasis were evaluated by functional experiments and clinical samples.

Results: Based on the gene expression profile analysis, we identified metastatic tumor cells acquired the mesenchymal-like characteristics and displayed the increased dependency on glutamine utilization. Further, the gain of NDRG2 function blocked epithelial-mesenchymal transition (EMT) and glutaminolysis, potentially through suppression of glutamine transporter ASCT2 expression. The ASCT2 restoration reversed NDRG2 inhibitory effect on EMT program and tumor metastasis. Mechanistic study indicates that NDRG2 promoted Fbw7-dependent c-Myc degradation by inhibiting Akt activation, and subsequently decreased c-Myc-mediated ASCT2 transcription, in both tumor and NDRG2-knockout MEF cells. Supporting the biological significance, the reciprocal relationship between NDRG2 and ASCT2 were observed in multiple types of tumor tissues, and associated with tumor malignancy.

Conclusions: NDRG2-dependent repression of ASCT2 presumably is the predominant route by which NDRG2 rewires glutaminolysis and blocks metastatic tumor survival. Targeting glutaminolytic pathway may provide a new strategy for the treatment of metastatic tumors.

Glutamine metabolism in Th17/Treg cell fate: applications in Th17 cell-associated diseases

Alteration in the Th17/Treg cell balance is implicated in various autoimmune diseases and these disease-associated pathologies. Increasing investigations have shown that glutamine metabolism regulates the differentiation of Th17 and Treg cells. Here we summarize the mechanisms by which glutamine metabolism regulates Th17/Treg cell fate. Some examples of a glutamine metabolism-dependent modulation of the development and progression of several Th17 Treg cell-associated diseases are provided afterward. This review will provide a comprehensive understanding of the importance of glutamine metabolism in the fate of Th17 Treg cell differentiation.

ROS-associated immune response and metabolism: a mechanistic approach with implication of various diseases

The immune system plays a pivotal role in maintaining the defense mechanism against external agents and also internal danger signals. Metabolic programming of immune cells is required for functioning of different subsets of immune cells under different physiological conditions. The field of immunometabolism has gained ground because of its immense importance in coordination and balance of immune responses. Metabolism is very much related with production of energy and certain by-products. Reactive oxygen species (ROS) are generated as one of the by-products of various metabolic pathways. The amount, localization of ROS and redox status determine transcription of genes, and also influences the metabolism of immune cells. This review discusses ROS, metabolism of immune cells at different cellular conditions and sheds some light on how ROS might regulate immunometabolism.

High methionyl-tRNA synthetase expression predicts poor prognosis in patients with breast cancer

Aims

Methionyl–tRNA synthetase (MARS) is known to play a critical role in initiating translation and protection against cellular damages in vivo. The aim of this study was to clarify the role of MARS in breast cancer (BC) progression.

Methods

The expressions of MARS messenger RNA (mRNA) and protein in human BC tissues and adjacent non-cancerous tissues were detected by quantitative real-time PCR, western blot and immunohistochemistry. The prognostic potential of MARS in patients with BC was assessed by univariate and multivariate survival analyses. The association between the MARS expression and BC progression was further evaluated by the bioinformatics database of UALCAN, Gene Expression Profiling Interactive Analysis (GEPIA) and Gene Expression Database of Normal and Tumor Tissues (GENT). The role of MARS in the proliferation, migration and epithelial-to-mesenchymal transition (EMT) of human breast cancer cell line (MCF-7 cells) was investigated after siRNA transfection.

Results

The expression level of MARS mRNA in the fresh BC tissues was significantly higher than that in the adjacent tissues. Immunohistochemistry showed that the expression level of MARS was closely associated with the clinicopathologial parameters of patients with BC, including the HER-2 status, Ki-67 status, molecular classification, tumour grade, N stage and tumour, node, metastasis (TNM) stage, and this finding was further confirmed by UALCAN database. The Kaplan-Meier analysis showed that high MARS expression and TNM stage were predictors of poor prognosis of patients with BC. The proliferation, migration and EMT capabilities of MCF-7 cells were significantly suppressed after MARS knockdown. An overview of UALCAN, GEPIA and GENT results suggested that MARS may be an oncogene of BC, as well as a potential therapeutic target of this malignant tumour.

Conclusions

High expression level of MARS in the human BC tissues was significantly associated with the unfavourable prognosis of patients with BC, suggesting that MARS may serve as a potential prognostic marker for the clinical diagnosis and prognostic prediction of BC.

OGDHL silencing promotes hepatocellular carcinoma by reprogramming glutamine metabolism

BACKGROUND & AIMS

Mitochondrial dysfunction and subsequent metabolic deregulation are commonly observed in cancers, including hepatocellular carcinoma (HCC). When mitochondrial function is impaired, reductive glutamine metabolism is a major cellular carbon source for de novo lipogenesis to support cancer cell growth. The underlying regulators of reductively metabolized glutamine in mitochondrial dysfunction are not completely understood in tumorigenesis.

METHODS

We systematically investigated the role of oxoglutarate dehydrogenase-like (OGDHL), one of the rate-limiting components of the key mitochondrial multi-enzyme OGDH complex (OGDHC), in the regulation of lipid metabolism in hepatoma cells and mouse xenograft models.

RESULTS

Lower expression of OGDHL was associated with advanced tumor stage, significantly worse survival and more frequent tumor recurrence in 3 independent cohorts totaling 681 postoperative HCC patients. Promoter hypermethylation and DNA copy deletion of OGDHL were independently correlated with reduced OGDHL expression in HCC specimens. Additionally, OGDHL overexpression significantly inhibited the growth of hepatoma cells in mouse xenografts, while knockdown of OGDHL promoted proliferation of hepatoma cells. Mechanistically, OGDHL downregulation upregulated the α-ketoglutarate (αKG):citrate ratio by reducing OGDHC activity, which subsequently drove reductive carboxylation of glutamine-derived αKG via retrograde tricarboxylic acid cycling in hepatoma cells. Notably, silencing of OGDHL activated the mTORC1 signaling pathway in an αKG-dependent manner, inducing transcription of enzymes with key roles in de novo lipogenesis. Meanwhile, metabolic reprogramming in OGDHL-negative hepatoma cells provided an abundant supply of NADPH and glutathione to support the cellular antioxidant system. The reduction of reductive glutamine metabolism through OGDHL overexpression or glutaminase inhibitors sensitized tumor cells to sorafenib, a molecular-targeted therapy for HCC.

CONCLUSION

Our findings established that silencing of OGDHL contributed to HCC development and survival by regulating glutamine metabolic pathways. OGDHL is a promising prognostic biomarker and therapeutic target for HCC.

LAY SUMMARY

Hepatocellular carcinoma (HCC) is one of the most prevalent tumors worldwide and is correlated with a high mortality rate. In patients with HCC, lower expression of the enzyme OGDHL is significantly associated with worse survival. Herein, we show that silencing of OGDHL induces lipogenesis and influences the chemosensitization effect of sorafenib in liver cancer cells by reprogramming glutamine metabolism. OGDHL is a promising prognostic biomarker and potential therapeutic target in OGDHL-negative liver cancer.

Targeting Hepatic Glutaminase 1 Ameliorates Non-alcoholic Steatohepatitis by Restoring Very-Low-Density Lipoprotein Triglyceride Assembly

Non-alcoholic steatohepatitis (NASH) is characterized by the accumulation of hepatic fat in an inflammatory/fibrotic background. Herein, we show that the hepatic high-activity glutaminase 1 isoform (GLS1) is overexpressed in NASH. Importantly, GLS1 inhibition reduces lipid content in choline and/or methionine deprivation-induced steatotic mouse primary hepatocytes, in human hepatocyte cell lines, and in NASH mouse livers. We suggest that under these circumstances, defective glutamine fueling of anaplerotic mitochondrial metabolism and concomitant reduction of oxidative stress promotes a reprogramming of serine metabolism, wherein serine is shifted from the generation of the antioxidant glutathione and channeled to provide one-carbon units to regenerate the methionine cycle. The restored methionine cycle can induce phosphatidylcholine synthesis from the phosphatidylethanolamine N-methyltransferase-mediated and CDP-choline pathways as well as by base-exchange reactions between phospholipids, thereby restoring hepatic phosphatidylcholine content and very-low-density lipoprotein export. Overall, we provide evidence that hepatic GLS1 targeting is a valuable therapeutic approach in NASH.

Berberine Inhibits Growth of Liver Cancer Cells by Suppressing Glutamine Uptake

Introduction

Glutamine metabolism is essential for the proliferation of cancer cells. Transported by SLC1A5, a Na⁺ dependent transporter, glutamine is absorbed for further use. Recent studies have revealed the anti-tumor effect of berberine. The present study aimed to evaluate the effect of berberine on cancer cell glutamine metabolism.

Materials and methods

The inhibitory effect of berberine on liver cancer cells was analyzed by CCK-8 and EdU assay. The glutamine concentrations were detected by ELISA and UHPLC-MRM-MS analysis. Glutamine metabolism-related proteins were determined by Western blot, immunofluorescent analysis and immunohistochemistry.

Results

Berberine inhibited the proliferation of Hep3B and BEL-7404 cell in vitro. Berberine suppressed the glutamine uptake by inhibiting SLC1A5. The upregulation of SLC1A5 led to an increased glutamine uptake and improved tolerance to berberine. Berberine suppresses SLC1A5 expression by inhibiting c-Myc. Furthermore, berberine suppresses the growth of tumor xenografts, and the expression of SLC1A5 and c-Myc in vivo. The high expression of SLC1A5 in hepatocellular carcinoma (HCC) tissues is associated with poor prognosis.

Conclusion

Berberine can suppress the proliferation of liver cancer cells by reducing SLC1A5 expression.

Glutamine Metabolism Is Essential for Stemness of Bone Marrow Mesenchymal Stem Cells and Bone Homeostasis

Skeleton has emerged as an endocrine organ which is both capable of regulating energy metabolism and being a target for it. Glutamine is the most bountiful and flexible amino acid in the body which provides adenosine 5′-triphosphate (ATP) demands for cells. Emerging evidences support that glutamine which acts as the second metabolic regulator after glucose exerts crucial roles in bone homeostasis at cellular level, including the lineage allocation and proliferation of bone mesenchymal stem cells (BMSCs), the matrix mineralization of osteoblasts, and the biosynthesis in chondrocytes. The integrated mechanism consisting of WNT, mammalian target of rapamycin (mTOR), and reactive oxygen species (ROS) signaling pathway in a glutamine-dependent pattern is responsible to regulate the complex intrinsic biological process, despite more extensive molecules are deserved to be elucidated in glutamine metabolism further. Indeed, dysfunctional glutamine metabolism enhances the development of degenerative bone diseases, such as osteoporosis and osteoarthritis, and glutamine or glutamine progenitor supplementation can partially restore bone defects which may promote treatment of bone diseases, although the mechanisms are not quite clear. In this review, we will summarize and update the latest research findings and clinical trials on the crucial regulatory roles of glutamine metabolism in BMSCs and BMSC-derived bone cells, also followed with the osteoclasts which are important in bone resorption.

Effect of glutaminase inhibition on cancer-induced bone pain

Purpose

The complex nature of cancer-induced bone pain (CIBP) has led to investigation into cancer-targeted therapies. This has involved targeting glutamate release from the tumor, secreted as a byproduct of antioxidant responses and metabolic disruption. Cancer cells undergo many metabolic changes that result in increased glutamine metabolism and subsequently the production of glutamate. Glutaminase (GLS) is the enzyme that mediates the conversion of glutamine to glutamate and has been shown to be upregulated in many cancer types including malignancies of the breast. This enzyme, therefore, represents another potential therapeutic target for CIBP, one that lies upstream of glutamate secretion.

Methods

A recently developed inhibitor of GLS, CB-839, was tested in an animal model of CIBP induced by intrafemoral MDA-MB-231 xenografts. CIBP behaviors were assessed using Dynamic Weight Bearing and Dynamic Plantar Aesthesiometer readings of mechanical hyperalgesia and allodynia.

Results

CB-839 failed to modulate any of the associated nociceptive behaviors induced by intrafemoral MDA-MB-231 tumor growth. Further investigation in vitro revealed the sensitivity of the drug is dependent on the metabolic flexibility of the cell line being tested which can be modulated by cell culture environment.

Conclusion

Adaptation to metabolic disturbances may explain the failure of CB-839 to exhibit any significant effects in vivo and the metabolic flexibility of the cell line tested should be considered for future investigations studying the metabolic effects of glutaminase inhibition.

Rewiring of the Human Mitochondrial Interactome during Neuronal Reprogramming Reveals Regulators of the Respirasome and Neurogenesis

Mitochondrial protein (MP) assemblies undergo alterations during neurogenesis, a complex process vital in brain homeostasis and disease. Yet which MP assemblies remodel during differentiation remains unclear. Here, using mass spectrometry-based co-fractionation profiles and phosphoproteomics, we generated mitochondrial interaction maps of human pluripotent embryonal carcinoma stem cells and differentiated neuronal-like cells, which presented as two discrete cell populations by single-cell RNA sequencing. The resulting networks, encompassing 6,442 high-quality associations among 600 MPs, revealed widespread changes in mitochondrial interactions and site-specific phosphorylation during neuronal differentiation. By leveraging the networks, we show the orphan C20orf24 as a respirasome assembly factor whose disruption markedly reduces respiratory chain activity in patients deficient in complex IV. We also find that a heme-containing neurotrophic factor, neuron-derived neurotrophic factor [NENF], couples with Parkinson disease-related proteins to promote neurotrophic activity. Our results provide insights into the dynamic reorganization of mitochondrial networks during neuronal differentiation and highlights mechanisms for MPs in respirasome, neuronal function, and mitochondrial diseases.

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Rewiring of mitochondrial (mt) protein interaction network in distinct cell states

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Dramatic changes in site-specific phosphorylation during neuronal differentiation

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C20orf24 is a respirasome assembly factor depleted in patients deficient in CIV

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NENF binding with DJ-1/PINK1 promotes neurotrophic activity and neuronal survival